On December 18, 2024, the Washington State Department of Agriculture (WSDA) announces the official eradication of the Northern Giant Hornet in Whatcom County and, by extension, the state. The news conference caps a five-year saga beginning when a nest was found and destroyed in Nanaimo, British Columbia, in August 2019, followed by the discovery of a dead specimen across the border in Blaine on December 8. Vespa mandarinia, then known as the Asian Giant Hornet – and more informally as the Murder Wasp, Yak Killer, or Murder Hornet – causes consternation ranging to panic. Not only is it alarming looking – up to 2 inches long, with powerful mandibles and a reusable barbed stinger – it is an aggressive predator to honeybees as well as wasps and its stings can be dangerous to humans. One domestic beehive in Custer, near Blaine, was found destroyed in November 2019, in what is later determined to be a Giant Hornet attack. Regional beekeepers and hundreds of other volunteers collaborated with the WSDA to monitor the newcomers and locate their nests. During the next two years, four nests, all in Whatcom County, were found and eliminated. No sightings were reported during 2023 and 2024, and after a final 22-week period involving 144 traps and other forms of observation, the WSDA announces victory.
An Efficient Predator
V. mandarinia are native to Asia, ranging from India, South China, and Japan to the Korean Peninsula. Primarily residents of forested areas near sea level, they attack both wild and domesticated bees and wasps, killing and eating both adults and larvae and also consuming the honey. They prefer to nest in tree cavities or in hollows in the ground, often at the base of trees. In the spring, mated queens who have been dormant over the winter will emerge to feed on tree sap before excavating a nest and beginning to lay eggs. When the first foraging wasps mature and emerge from the nests, usually around July, scouts head out to locate hives and mark them with pheromones. Other wasps from that nest follow the scent trail and attack the hives. A group of a dozen to 20 hornets can destroy a beehive in an hour.
When the slaughter is complete, the hornets roll the corpses into ball-shaped clumps and carry them to their nest to feed the larvae, which in turn secrete a gooey substance that is eaten by the adults. Strong and fast flyers, the hornets can travel at least five miles in search of prey.
Asian beekeepers have developed a number of strategies to protect their bees. The simplest is to station people around the hives to beat the attackers with sticks. Other methods include traps baited with fermented rice wine and screens over the hives to prevent entrance. None are fully effective. The Asian honeybee, which is a different species than the European honeybee used in North American apiaries, has itself developed a defense. When a hornet scout appears at the hive, a few hundred bees will emerge and surround it, forming a buzzing, vibrating ball that over about an hour can achieve and maintain an internal temperature of 115 degrees Fahrenheit. That is enough to kill the wasp while allowing the bees, at least most of them, to survive. The hive is then safe until the next scout finds it. Domestic honeybees in the United States and Canada do not have this adaptation.
Humans are the species' only predator. Many hornets are killed by beekeepers, and many more are killed in the quest for specialty cuisine, especially in the central Japanese region of Chibu. Grubs are fried or steamed, while the adults are skewered like kabobs or drowned in a distilled liquor called shochu, adding a tingling kick to the drink.
An Unknown Journey
The first nest found in North America was in Robins Park in Nanaimo, British Columbia, on Vancouver Island. Local beekeepers used location data from a hornet sighting in July to approach it. Although it was just five feet from a public walking trail, no one was bothered until John and Moufida Holubeshen identified it in August. John was stung on approach to the nest, saying the size and velocity of the attacker made it feel like getting hit in the chest with a plank. Nevertheless, the Holubeshens returned the next night with two other beekeepers and destroyed the nest. The next confirmed North American sighting was made soon after, via photograph, in White Rock, just north of the U.S. border.
The first U.S. report of the hornets in the wild was from Blaine, where a resident walked outside on December 8, 2019, and saw an unfamiliar creature on his doorstep. "It looks like a toy," said WSDA entomologist Sven-Eric Spichiger. "It's a freakishly large hornet with a giant head." Workers from the department drove up from Olympia that week to collect it. By December 14 the state had received official confirmation from the USDA of the unwelcome U.S. first. That identification in Blaine solved a mystery for Ted McFall, a longtime beekeeper in nearby Custer, who had found one of his hives destroyed the previous month. On a routine check, he saw "thousands of bee bodies strewn on the ground outside of the hive" (Baker, "The Arrival ..."). Inside the hive was more carnage, piles of decapitated bees, and no survivors. McFall said it was the first time in his experience that his bees had been unable to mount even a token defense. Not a single dead attacker was visible.
The hornet's route to North America is unknown. Only a queen could establish a new hive on a new continent, and queens are active outside their nests for only a fairly brief period. One theory is that hornet queens in Asia have settled in shipping containers for their winter dormancy and then awakened across the ocean. One mated queen can establish an entire colony, and that colony would produce more queens to continue the advance. Another possible transmission route is through the shipping of live larvae for aficionados of wasps as food or as traditional medicine. This is illegal but not unknown. A package containing an entire V. mandarinia nest, including live larvae and pupae, was intercepted at a U.S. port of entry at some point before 2010, according to Allen Smith-Pardo, an entomologist with the USDA.
"This is Our Window"
However they got here, once they were spotted, the Department of Agriculture and regional beekeepers mounted reporting and tracking systems to monitor the spread and, if possible, eliminate the hornets.
"This is our window to keep it from establishing," Chris Looney, an entomologist with the WSDA, told The New York Times (Baker, "Murder Hornets..."). "If we can't do it in the next couple of years, it probably can't be done." Distribution modeling done at Washington State University suggested that much of Western Washington and in fact much of North America is good V. mandarinia habitat, and residents nationwide began looking at all kinds of flying insects with more alarm than usual.
Somewhat similar-looking native species including yellow jackets, native elm sawflies, bumblebees, and cicada killer wasps all led to reports that were dutifully recorded on a WSDA interactive map. The hornets became instant media celebrities, sparking the creation of memes and jokes pairing them with another notorious 2020 newcomer, the coronavirus causing COVID-19. University of Illinois entomologist May Berenbaum told The Associated Press science writer Seth Borenstein that "people are afraid of the wrong thing ... If anyone's a murder insect, it would be a mosquito." Berenbaum chalked up some of the concern over the hornets to the trauma of the coronavirus pandemic. "This year is unbelievable in a horrible, horrible way. Why shouldn't there be murder hornets?" she said (Borenstein).
Citizen Scientists Set Traps
In addition to the public reporting system, the WSDA along with beekeepers associations and other volunteers began more formal tracking methods in early 2020. These included "sap traps," squares of sticky material placed on sap-producing trees in April, in the hopes of trapping queens as they stocked up on nutrients before descending into their nests to start laying eggs. Since only the queens are out during this period, the chance of capture was slim but the potential payoff was great. Killing a queen dooms an entire colony.
Once worker wasps had hatched and matured enough to emerge and begin predation, traps baited with a mixture of orange juice and rice cooking wine were placed around apiaries and likely nest sites. The WSDA recruited volunteers to make and monitor traps anywhere in the state, but particularly in the Northwest Washington counties of Whatcom, Skagit, Island, San Juan, Clallam, and Jefferson. Thirty-eight apiaries in Whatcom County alone, spearheaded by the Mount Baker Beekeepers Association, joined the effort to track and eliminate the invader. Residents also signed up to monitor the nests of paper wasps, a popular hornet food source. Each volunteer committed to checking a nearby nest weekly and recording any sign of hornets. Other monitoring efforts involved radio-tagging live-captured wasps in order to track them back to the nest area, and using thermography sensors to locate underground nests by their heat differential to the outside air, especially at night.
The first nest was located near Blane in October 22, 2020, and eradicated days later. The WSDA workers in their Amazon-purchased protective gear became instant media heroes. "A dozen humanoid forms encased in full-body, white nylon suits are working on scaffolding at the base of a saran-wrapped tree by the red glow of headlamps, one of them raising a plexiglass vacuum tube between its blue-gloved hands in triumph," wrote Megan Molteni in Wired magazine.
No more nests were found until the next summer, when three more were located in north Whatcom County on August 19, September 9, and September 23. All were eradicated, providing compelling video for observers and useful insect samples for researchers around the world. Karla Salp, communications specialist for the WSDA, said that the public had reported half of the confirmed northern giant hornet sightings in Washington, and had a hand, either directly or indirectly, in all four of the nests. Monitoring continued through November that year and resumed in 2023, but no more nests or individual giant hornets have been sighted since.
